This is a great 3-axis compass module for your Arduino autonomous robot to help it find its path in life! It is designed to be easy to use and fully compatible with Arduino Uno, Mega and Nano.

This compass module also provides you with the asimuth to help simplify things even more. An azimuth value of '45' would imply 45NE and is essentially the 0-360 degree value you are used to seeing on a compass. Though, if you want to know the exact angle in the X, Y and Z directions to do more advanced sensing then this unit is perfect for you as well.

An easy to use library is available here: https://github.com/keepworking/Mecha_QMC5883L 

A tutorial and guide can be found here: http://henrysbench.capnfatz.com/henrys-bench/arduino-sensors-and-input/arduino-gy-273-hmc5883l-magnetometer-compass-tutorial/